Why isn't backface-hidden working on iPhone?

Question

I have this code.

HTML:

.flip-card {
  background-color: transparent;
  width: 300px;
  height: 376px;
  perspective: 1000px;
  border-radius: 1rem;
  margin: 0 auto 1.5rem;
  transform-style: preserve-3d;
}

.flip-card:hover .flip-card-inner,
.flip-card:active .flip-card-inner {
  transform: rotateY(180deg);
}

.flip-card-front,
.flip-card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  /* Safari */
  backface-visibility: hidden;
}

.flip-card-front {
  background-color: #bbb;
  color: black;
}

.flip-card-back {
  background: linear-gradient(180deg, rgba(0, 0, 0, 0.5) 0%, rgba(44, 52, 145, 0.5) 100%), var(--secondary);
  color: white;
  transform: rotateY(180deg);
  border-radius: 1rem;
  box-shadow: 0 4px 2rem rgba(0, 0, 0, 0.5);
}

.flip-card-back p {
  font-size: 16px;
  padding: 1.5rem;
  margin-top: 3rem;
  color: #333;
}

.avatar {
  width: 250px;
  position: relative;
  top: 0;
  left: 0;
  z-index: 1;
  backface-visibility: hidden !important;
  margin: auto;
  border-radius: .75rem;
}

.avatar img {
  backface-visibility: hidden !important;
}

.flip-card-front {
  background-color: #fff;
  color: black;
  border-radius: 1rem !important;
  backface-visibility: hidden !important;
  box-shadow: 0 0 1rem rgba(0, 0, 0, 0.125);
  padding: 1rem;
}

.flip-card-inner {
  position: relative;
  width: 280px;
  height: auto;
  text-align: center;
  transition: transform 0.8s;
  transform-style: preserve-3d;
  border-radius: 1rem;
  min-height: 360px;
}

.nameCharge {
  position: relative;
  z-index: 200;
  top: 0;
  left: 0;
  display: block;
  backface-visibility: hidden !important;
  padding: 1rem 0;
}

.nameCharge h3 {
  text-transform: capitalize;
  font-family: 'Montserrat', Helvetica, sans-serif;
  font-size: 18px;
  color: #1F5CE5;
  font-weight: 600;
  margin: 0;
  backface-visibility: hidden;
  text-align: left;
}

.nameCharge h4 {
  font-size: 12px;
  text-align: left;
  font-weight: 600;
  color: #3b3b3b;
}

<div class="flip-card ">
  <div class="flip-card-inner ">
    <div class="flip-card-front ">

      <img src="https://via.placeholder.com/300" alt="blah" class="avatar ">

      <div class="nameCharge ">
        <h3>The Name</h3>
        <h4>The Position</h4>
      </div>

    </div>
    <div class="flip-card-back ">

      <p>text text text</p>

    </div>
  </div>
</div>

This code works fine on desktop devices, but for some reason, on iPhone the front image is visible when I flip the card. I could reproduce this behavior on iPhone, Android seems to work as expected

What am I missing here?